Background
    In temperate latitudes, most coastal invertebrates living on or in the sediment (i.e., "benthic" organisms such as clams, crabs, worms and snails) spawn their gametes or larvae into the water column where they drift for hours to months before settling back down onto the seafloor, metamorphosing, and assuming an entirely benthic existence. The planktonic larval stage is critical in the life histories and population dynamics of benthic organisms because it is the primary dispersal stage, and thus is responsible for colonizing new habitat or replenishing established populations. This CoOP research program focused on benthic invertebrates which live as adults in sandy, nearshore sediments and whose planktonic larvae disperse for approximately one month across waters of the inner continental shelf defined here as the region roughly from just off the beach to several kilometers offshore, typically depths of less than 30 meters.

    The basic hypothesis guiding the research was that planktonic larvae of nearshore-dwelling organisms exploit the vertical variation of inner-shelf circulation to control their cross-shelf transport. This control is expected to be species-specific, depending on the extent of acceptable adult habitat. Thus, the planktonic larvae of invertebrates confined as adults to the sandy beach-face may exert more active control over their vertical distributions in the water column than larvae of sandy, subtidal species for which there is a broader band of acceptable adult habitat across the inner shelf. The research questions included the following: (1) Is the timing of gamete release correlated with suspension and offshore transport events?; (2) What are the temporal variations in vertical distributions of larvae and how are these related to physical features of the environment and behaviors of the organisms?; (3) What physical processes contribute to the evolution of the cross-shelf distribution of larvae?; and (4) What is the relationship between larval supply, boundary-layer processes and settlement?

    The study also addressed several fundamental research problems in physical oceanography and sediment transport in order to investigate plausible mechanisms for larval dispersal. These included studies of: (1) the dominant terms (e.g., wind, waves, pressure gradients) in the along-shelf momentum balance; (2) the processes influencing the vertical and cross-shelf structure of the cross-shelf velocity field; (3) the processes influencing the temporal evolution and vertical and cross-shelf structure of the density field; (4) the hydrodynamics of wave/current bottom boundary layers; and (5) the suspension of inorganic and organic particulates resulting from boundary-layer processes.

    The field study involved measurements of the spatial and temporal distributions of planktonic larvae of selected organisms, and the physical and sedimentological parameters likely to affect their transport off of and onto the inner shelf. The study site was on the North Carolina shelf between Chesapeake Bay and Oregon Inlet, focusing on the inner shelf near Duck. Field observations were made during two intensive one-month periods in 1994, representing times of relatively strong stratification and weak winds (August) and of weak stratification and strong wind events (October).

Principal Investigators
Steve Lentz, Woods Hole Oceanographic Institution;
Cheryl Ann Zimmer (Butman), UCLA Biology (formerly Woods Hole)
Robert T. Guza and John L. Largier, Scripps Institution of Oceanography, Center for Coastal Studies;
Ole S. Madsen, Massachusetts Institute of Technology;
Alan L. Shanks, UO, Oregon Institute of Marine Biology;
John Brubaker and L. Donelson Wright, Virginia Institute of Marine Science

Publications  (reprints available by contacting the authors)

1. Butman, C.A. (1994). CoOP: Coastal Ocean Processes Study. Interdisciplinary approach, new technology to determine coupled biological, physical, geological processes affecting larval transport on inner shelf. Sea Technology, pp. 44-49.

2. Gallagher, E.L., W. Boyd, S. Elgar, R.T. Guza and B. Woodward (1996). Performance of a sonar altimeter in the nearshore. Marine Geology, 133:241-248.

3. Raubenheimer B. and R.T. Guza (1996). Observations and predictions of run-up. J. Geophys. Res., 101(C10):25575-25587.

4. Raubenheimer, B., R.T. Guza and S. Elgar (1996). Wave transformation across the inner surf zone. J. Geophys. Res., 101(C10):25589-25597.

5. Chapman, D.C. and S.J. Lentz (1997). Adjustment of stratified flow over a sloping bottom. J. Phys. Oceanogr., 27(2):340-356.

6. Chen, Y., R.T. Guza and S. Elgar (1997). Modeling spectra of breaking surface waves in shallow water. J. Geophys. Res., 102(C11): 25035-25046.

7. Elgar, S., R.T. Guza, B. Raubenheimer, T.H.C. Herbers and E.L. Gallagher (1997). Spectral evolution of shoaling and breaking waves on a barred beach. J. Geophys. Res.,102(C7):15797-15805.

8. Kim, S.C., L.D. Wright and B.O. Kim (1997) The combined effects of synoptic-scale and local-scale meteorological events on bed stress and sediment transport on the inner shelf of the Middle Atlantic Bight. Cont. Shelf Res., 17: 407-433.

9. Vanhoff, B., S. Elgar and R.T. Guza (1997). Numerically simulating nongaussian sea surfaces. J. Waterway, Port, Coastal and Ocean Eng., March/April 1997:68-72.

10. Feddersen, F., R.T. Guza, S. Elgar and T.H.C. Herbers (1998). Alongshore momentum balances in the nearshore. J. Geophys. Res., 103(C8): 15667-15676.

11. Gallagher, E.L., S. Elgar and R.T. Guza (1998). Observations of sand bar evolution on a natural beach. J. Geophys. Res., 103(C2): 3203-3215.

12. Shanks, A.L. (1998). Abundance of post-larval Callinectes sapidus, Penaeus spp., Uca spp., and Libinia spp. collected at an outer coastal site and their cross-shelf transport. Mar. Ecol. Prog. Ser.,168: 57-69.

13. Shay, L.K., S.J. Lentz, H.C. Graber and B.K. Haus (1998).  Current structure variations detected by high frequency radar and vector measuring current meters. J. Atmos. Oceanic Tech.,15(1) Part 2: 237-256.

14. Austin, J.A. (1999). The role of the alongshore wind stress in the heat budget of the North Carolina inner shelf. J. Geophys. Res.,104(C8): 18187-18203.

15. Austin, J.A. and S.J. Lentz (1999). The relationship between synoptic weather systems and meteorological forcing on the North Carolina inner shelf.  J. Geophys. Res.,104(C8):18159-18185.

16. Herbers, T.H.C., S. Elgar and R.T. Guza (1999). Directional spreading of waves in the nearshore.  J. Geophys. Res., 104(C4):7683-7693.

17. Lentz, S., R.T. Guza, S. Elgar, F. Feddersen and T.H.C. Herbers (1999). Momentum balances on the North Carolina inner shelf.  J. Geophys. Res.,104(C8):18205-18226.

18. Rennie, S.E., J.L. Largier and S. J. Lentz (1999). Observations of a pulsed buoyancy current downstream of Chesapeake Bay. J. Geophys. Res.,104(C8):18227-18240.

19. Lentz, S. and B. Raubenheimer (1999). Field observations of wave setup. J. Geophys. Res., 104(C11):25867-25875.

20. Feddersen, F., R.T. Guza, S. Elgar and T.H.C. Herbers (2000) Velocity moments in alongshore bottom stress parameterizations. J. Geophys. Res., 105: 8673-8686.

21. Shanks, A.L., J. Largier, L. Brink, J. Brubaker and R. Hooff (2000) Demonstration of the onshore transport of invertebrate larvae by the shoreward movement of an upwelling front. Limnol. Oceanogr., 45: 230-236.

22. D'Sa, E., S.E. Lohrenz, J.H. Churchill, V. Asper, J. Largier and A.J. Williams, III (2001) Chloropigment distribution and transport on the inner shelf off Duck, North Carolina. J. Geophys. Res., 106: 11581-11596.

23. Cudaback, C.N. and J.L. Largier (2001) The cross-shelf structure of wind-and buoyancy-driven circulation over the North Carolina inner shelf. Cont. Shelf Res., 21: 1649-1668.

24. Lentz, S.J. (2001) The influence of stratification on the wind-driven cross-shelf circulation over the North Carolina shelf. Journal of Physical Oceanography 31: 2749-2760. (3) Lentz, S.J., M. Carr, and T.H.C. Herbers, 2001. Barotropic tides on the North Carolina shelf. J. Phys. Ocean., 31: 1843-1859.

25. Lentz, S.J., M. Carr and T.H.C. Herbers (2001) Barotropic tides on the North Carolina shelf. J. Phys. Ocean., 31:1843-1859.

26. Austin, J.A. and S.J. Lentz (2002) The inner shelf response to wind-driven upwelling and downwelling. J. Phys. Ocean., 32: 2171-2193.

27. Shanks, A.L., J. Largier, L. Brink, J. Brubaker and R. Hooff (2002) Observations on the distribution of meroplankton during a downwelling event and associated intrusion of the Chesapeake Bay estuarine plume. J. Plankton Res., 24: 391-416.

28. Garland, E.D. and C.A. Zimmer (2002) Techniques for the identification of bivalve larvae. Mar. Ecol. Prog. Ser., 225: 299-310.

29. Garland, E.D. and C.A. Zimmer (2002) Hourly variations in planktonic larval concentrations on the inner shelf: Emerging patterns and processes. J. Mar. Res., 60: 311-325.

30. Garland, E.D., C.A. Zimmer and S.J. Lentz (2002) Larval distributions in inner-shelf waters: The roles of wind-driven cross-shelf currents and diel vertical migrations. Limnol. Oceanogr., 47: 311-325.

31. Lentz, Steven J., Steve Elgar and R. T. Guza.(accepted) Observations of the flow field near the nose of a buoyant coastal current. J. Phys. Ocean.

For additional information on the CoOP Duck Project, please visit the PVLAB DATA SITE

updated 20 December 2002